Welcome to the Corvette Forums at the Corvette Action Center!

Fuel Pressure Question 1988 C4

MatthewMI

Member
Joined
Nov 16, 2016
Messages
19
Location
Lansing, MI
Corvette
1988 35th Anniversary
Guys,
I have a weird issue with fuel pressure on a 1988 C4. Just put the car back together (it came in boxes) so it is fresh from the intake manifold up. New injectors were there when I got it, put them back in (I kno, I should have checked to see exactly what they were). New fuel pressure regulator and fuel pump/sock when reassembled as well as fuel filter. When firing, found the pulse dampener was bad, replaced with hose and was able to hold 40 LBS of pressure at the rail. It would hold the pressure for more than 30 minutes. Fired the car after an extended crank and let it warm up. Ran well. On the next firing which was cold, the crank was extended and a hard start. Checked the rail pressure and it got pressure at the 2 second prime but them bled off in 30 seconds and it seems to have a miss. Last night I had the same bleed of fuel pressure cold, started hard, miss is there still. Fuel pressure 38 LBS at idle. But, when i shut it down some what warm now, the fuel pressure stayed high... for as long as I cared to look at it.

Any ideas? Maybe the cold start valve? I neglected to clean it when I pulled the manifold (never crossed my mind) but did flush some nasty fuel from the fuel rail and lines. Maybe a sticky injector from the nasty in the fuel rail that flushed itself out while running?

I'll try to see if it holds pressure cold tonight.
Thanks!
Matt
 

dougelam

Well-known member
Joined
Jul 19, 2011
Messages
453
Location
Michigan
Corvette
2002 Roadster
I would chase the miss first
You didn't say if the miss was at all times, under load or just at idle

Sent from my SM-N920P using Tapatalk
 

MatthewMI

Member
Joined
Nov 16, 2016
Messages
19
Location
Lansing, MI
Corvette
1988 35th Anniversary
I would chase the miss first
You didn't say if the miss was at all times, under load or just at idle

Sent from my SM-N920P using Tapatalk
The car is on jack stands but seems to be consistent as much as I can replicate in the current situation. Right in the middle of an interior refresh so can't actually shut the doors right this moment.
 

MatthewMI

Member
Joined
Nov 16, 2016
Messages
19
Location
Lansing, MI
Corvette
1988 35th Anniversary
I would chase the miss first
You didn't say if the miss was at all times, under load or just at idle

Sent from my SM-N920P using Tapatalk
So here is what I pulled out of the car for a plug and what I was told should be in the car for a plug...
 

Attachments

  • IMG_3783.jpg
    IMG_3783.jpg
    260 KB · Views: 19

dougelam

Well-known member
Joined
Jul 19, 2011
Messages
453
Location
Michigan
Corvette
2002 Roadster
What a good start😀

Sent from my SM-N920P using Tapatalk
 

dougelam

Well-known member
Joined
Jul 19, 2011
Messages
453
Location
Michigan
Corvette
2002 Roadster
Yes, very wrong

Sent from my SM-N920P using Tapatalk
 

MatthewMI

Member
Joined
Nov 16, 2016
Messages
19
Location
Lansing, MI
Corvette
1988 35th Anniversary
So, all plugs but number 8 looked ok.
8 is fouled
I pulled cold start injector and fire with injector tester, no fuel. Pulled and cleaned, still no fuel.

My my theory is the number 8 injector got a little of the nasty in the fuel rail in it. That was causing that injector to leak sporadically. It is ok right now. Then I think no fuel from cold start is causing my hard start cold / poor idle cold.

So now now the question is, can that cold start be cleaned?
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
So here is what I pulled out of the car for a plug and what I was told should be in the car for a plug...

The top plug in that image is a 3/4-reach, flat seat plug for L98 aluminum heads. The bottom plug is a .460-in reach, taper seat plug, for cast iron heads which were not used on Corvette after MY86.

If the car is an 88, unless it has an incorrect engine with iron heads, DO NOT use the bottom plug.

Finally, the plug you took out looks damaged. I'd replace all 8 plugs before moving on to the fuel pressure issue.
 
Last edited:

MatthewMI

Member
Joined
Nov 16, 2016
Messages
19
Location
Lansing, MI
Corvette
1988 35th Anniversary
The top plug in that image is a 3/4-reach, flat seat plug for L98 aluminum heads. The bottom plug is a .460-in reach, taper seat plug, for cast iron heads which were not used on Corvette after MY86.

If the car is an 88, unless it has an incorrect engine with iron heads, DO NOT use the bottom plug.

Finally, the plug you took out looks damaged. I'd replace all 8 plugs before moving on to the fuel pressure issue.

Thank you, appreciate the input. Plugs are done now, runs better warm but that cold start valve is toast. Waiting for a replacement now.
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom